Platform leveling device

ABSTRACT

A platform leveling device for use on apparatuses with hoisting means and the like and comprising platform suspension means for movably attaching the platform to the apparatus, leveling means operably connected between the platform and the suspension means for maintaining a constant attitude of the platform during a hoisting operation regardless of the load distribution on the said platform.

PATENTED BEBB 1 I974 SHEET 2 BF 5 PATENTEI] UEB3 1 I974 SHEET 3 BF 5 PATENTED UECBI I974 SHEET 5 [1F 5 PLATFORM LEVELING DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to platform leveling devices and more particularly but not by way of limitation, to a platform leveling device for a boat hoisting apparatus. The device is particularly designed for maintaining a constant platform attitude while the boat and platform are being raised out of the water.

2. Description of the Prior Art.

With the present increase in leisure time for the average citizen and with the development of new lakes and harbor marinas there has been a substantial increase in the number of boats being stored in rental slips or the like. It has also been found to be desirable to get the boat out of the water or dry dock the boat, when it is not going to be used for some time. In the past, rather elaborate overhead hoisting apparatuses were used to lift the boat out of the water or the boat was simply left in the water to collect algae, barnacles or the like, on

the hull thereof.

Recent developments in dry docking apparatuses, such as that disclosed in the US. Pat. to Rutter, No. Re. 27,090, issued in 1971, have shown a move toward floating the boat out of the water by the use of submersible pontoons being connected to a hositing platform. With the platform and attached pontoons being submerged, the boat may be driven thereon and then lifted out of the water by simply forcing air into the submerged tanks of the pontoons. However, there has been a problem in using the submerged pontoons for floaters in that when the weight of the boat is not evenly distributed on the platform means, the boat and platform begins to tilt which can be catastrophic since the air in the partially filed pontoons will tend to move .toward the elevated end thereof which causes the out of level condition to worsen.

SUMMARY OF THE INVENTION The present invention contemplates a novel platform leveling device designed and constructed for overcoming the disadvantages inherently present in a platform hoisting system, and particularly those hoisting systems using floating pontoons or the like for lifting the platform out of the water. Two embodiments of the present invention utilize a plurality of fluid operated cylinders which are interconnected in a way to provide equal travel of each element of the suspension means when the platform is being moved. Three other embodiments herein contained utilize a mechanical linkage with torsion bars to provide equal travel for each element of the suspension means while another embodiment utilizes cable and pulley arrangements to provide equal travel of each element of the suspension means. By utilizing leveling means which are separate from the hoisting mechanism itself allows the said hoisting means, or floatable pontoons to be very simply constructed hence more reliable. The simplicity of the deisgn of the leveling apparatus and the several embodiments thereof would allow most boating enthusiasts to be able to afford to provide a hoisting apparatus for their boats so that they may be dry docked and held in place while the boat is not in use. This leveling device would also provide proper attitude for the boat while it is being lowered into the water or if the hositing apparatus, hoisting as the pontoons develop leaks and sink, the leveling device would let the boat into the water in a level position to prevent sinking thereof.

DESCRIPTION OF THE DRAWINGS Other and further advantageous features of the present invention will hereinafter more fully appear in connection with a detailed description of the drawings in which:

FIG. 1 is a prospective view of a hydro-hoisting apparatus equipped with aleveling device embodying the present invention.

FIG. 2 is an alternate leveling device which may be used on the movable platform of FIG. 1.

FIG. 3 is also a mechanical leveling device which may be utilized on the hydro-hoisting platform of FIG. 1.

FIG. 4 is a hydro-hoisting platform apparatus particularly designed for large boats such as cabin cruisers or the like, and is provided with a leveling device embodying the present invention.

FIG. 5 represents a hydro-hoist platform (hoisting tanks not shown) having a cable and pulley type leveling device which embodies the present invention.

FIG. 6 depicts a mechanical leveling device which may be used on the movable platform of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings in detail reference charac ter 10 generally indicates a platform leveling device which is operably connected to and used on a hydro hoist boat platform generally indicated by reference character 12. The hydro hoist platform 12 comprises a substantially rectangular shaped frame member 14 having a centrally disposed cross bar 16 thereacross. A pair of substantially identical longitudinally disposed elongated pontoon members 18 and 20 are secured to the bottom of the frame member 14 in any well known manner such as by bolts and the like. A pair of longitudinally disposed elongated cradle members 22 and 24 are secured to the frame member 14 at one end thereof carrying the stern portion of a boat thereon. The opposite end or forward end of the frame member 14 is provided with a substantially V-shaped cradle member 26 for carrying the bow portion of the boat thereon. A pair of substantially rectangular shaped bracket members 28 and 30 are secured to the frame member 14 adjacent to the opposite ends of the centrally disposed cross member 16. The hydro hoist frame assembly 12 is disposed within a boat slip or the like, and supported by a stationary dock structure 32 on one side and a second such dock structure (not shown) on the opposite side of the frame member 14.

An adjustable bracket member 34 is secured to the dock structure adjacent to one side of the frame member 14 and at one end thereof. A substantially identical bracket member (not shown) is oppositely disposed and secured to the opposite dock member adjacent to the forward end of the frame 14. An elongated adjustable bracket member 36 is secured to the dock structure 32 adjacent to the rear portion of the frame member 14, the said bracket member 36 being provided with a pair of longitudinally disposed spaced bars 38 and 40 for a purpose that will be hereinafter set forth. A second substantially identical elongated bracket member (not shown) is secured to the opposite dock structure (not shown) adjacent to the rear opposite edge of the frame member 14.

The bracket member 34 is provided with an adjustable rod 35 thereon the said rod 35 being provided with an aperture 37 therethrough for a purpose that will be hereinafter set forth.

The platform leveling device generally comprises a substantially triangular shaped elongated lever arm member 42 which is hingedlysecured by one corner thereof to the upper forward corner of the rectangular frame member 30 by means of a horizontally disposed pin member 44. The forward corner of the triangular lever arm 42 is provided with an outwardly extending connection rod 46 which is pivotally disposed within the aperture 37 of the bracket means 34. A second sub stantially identical elongated triangular shaped lever arm member 48 has one corner thereof pivotally secured to the rear lower corner of the rectangular frame member 30 by means of a pin member 50, the rearwardly extending apex of the lever arm member 48 being provided with an outwardly extending attachment rod52 which is slidably disposed between the spaced bracket bars 38 and 40 of the adjustable bracket 36,.

A first hydraulic cylinder 54 is secured to the frame member 14 and longitudinally disposed between the lower free corner of the elongated lever arm member 42 and the upper free corner of the elongated lever arm member 48. The hydraulic cylinder 54 is provided with an elongated connector rod 56 which extends completely through the hydraulic cylinder 54 and out of each end thereof. A piston member 58 is slidably disposed within the cylinder 54 and secured to the connector rod 56. One end of the connector rod 56 is pivotally secured to the lower free corner of the elongated lever arm member 42 by means of a pin 60 the opposite end of the connector arm 56 being pivotally secured to the upper free corner of the elongated lever arm member 48 by means of a pin 62.

Therefore, when the platform member 14 is raised, the elongated lever arm 42 will rotate in a counterclockwise direction about its pivot point 44 thereby pushing the connector rod 56 and associated piston member 58 toward the right side of the cylinder 54 as shown in FIG. 1. It is therefore obvious that the connector rod 56 will simultaneously push against the pin connector 62 which will rotate the elongated lever arm member 48 in a clockwise direction about the pin member 50 thereby simultaneously raising the rear end of the platform frame 14 by an amount substantially equal to that of the front portion of the platform 14. The rearwardly extending elongated lever arm member 48 is able to compensate for its rotational movement by having its connection rod 52 slidably disposed between the spaced bracket members 38 and 40 of the adjustable bracket 36. The leveling device 10 also comprises a third triangular shaped elongated lever arm member 64 which is substantially identical to the bar 42 and is pivotally secured tov the forward upper corner of the frame member 28 by means of a pin 66. The forwardly extending apex of the lever arm 64 is provided with an outwardly extending connection rod 68 for connecting the said lever arm 64 to a bracket member (not shown) which is substantially identical to the bracket member 34. A fourth triangular shaped elongated lever arm member 70 which is substantially identical to the lever arm bar 48 is pivotally secured to the lower rear corner of the frame member 28 by a horizontally extending pin member 72. Likewise, the rearwardly extending apex of the lever arm member is provided with an outwardly extending connection rod 74 which is reciprocally connected to a bracket member (not shown) which is substantially identical to the bracket member 36.

A second hydraulic cylinder 76 is secured to the frame member 14 and is longitudinally disposed between the lower free corner of the elongated lever arm member 64 and the upper free corner of the elongated lever arm member 70. The hydraulic cylinder 76 is provided with an elongated horizontally disposed connector rod 78 which extends completely through the hydraulic cylinder 76, one end of the connector rod 78 being pivotally secured to the free lower corner of the lever arm member 64, the opposite end of the connector arm 78 being pivotally secured to the upper free corner of the lever arm member 70. A piston member 80 is reciprocally disposed within the cylinder 76 and is secured to substantially the midpoint of the connector rod 78.

Therefore, it is readily apparent that when the platform member 14 is raised, the elongated lever arm 64 will rotate in a counterclockwise direction about its pivot point 66 thereby pushing the connector rod 78 and its associated piston member 80 toward the right side of the cylinder 76 as shown in FIG. 1. The connector rod 78 will simultaneously push against the upper free corner of the lever arm member 70 thereby causing the said lever arm 70 to rotate in a clockwise direction about the pin member 72 which causes the rear end of the platform frame 14 to raise by an amount substantially equal to that of the front portion of the platform 14.

The front portion of the hydraulic cylinder 76 is operably connected in open communication with the rear portion of the cylinder 54 by means of a hydraulic line 82, whereas the rear portion of the hydraulic cylinder 76 is operably connected in open communication with the front portion of the cylinder 54 by means of a hydraulic line 84. Hence, if there is any out-of-balance condition of the platform when it is being raised, or lowered due to uneven weight distribution of the boat carried thereon or due to one pontoon filling with air faster than the other, equalization is maintained by the hydraulic cylinder cross connection hereinbefore described. Stated another way, if the forward left hand portion of the frame member 14 is pressed downwardly thereby causing the lever arm bar 64 to rotate in a clockwise'direction and the rearwardly disposed lever arm bar 70 to rotate in a counterclockwise direction, this causes the piston member 80 to move forwardly within the cylinder 76. As the piston member 80 moves forward in the cylinder 76, hydraulic fluid is pushed out of the front portion of the cylinder 76 and is piped directly to the rear portion of the cylinder 54 which in turn causes the piston 58 of the cylinder 54 to be pushed forward in a like manner. This cross-over action will serve to maintain a substantially constant attitude of the entire platform frame member 14 while the said platform is eiher being raised or lowered or is in a static condition. a v

it is noted thatfor ease of installation of the platform leveling device 10, the lever arm bars 42, 48, 64 and 70 are pivotally mounted also for rotation in a horizontal plane by means of vertically disposed pin members 86, 88, and 92, respectively. Locking bars 94 and 96 are provided for the lever arm bars 64 and 70, respectively,

' to lock the said lever arm bars into place when the leveling device is in position for use. The lever arm bars 42 and 48 are provided with substantially identical locking devices which are not shown. It is again noted that the entire platform frame with associated suspension and leveling means is vertically adjustable with respect to the adjacent dock 32 by means of the brackets 34 and 36 and their oppositely disposed counter parts (not shown).

Referring now to FIG. 2, reference character 98 generally indicates a suspension and leveling means for the hydro-hoist apparatus depicted in FIG. 1. However, the suspension and leveling apparatus 98 is of the torsion bar type rather than hydraulic, as will be hereinafter set forth. The suspension and leveling device 98 generally comprises a pair of spaced rectangular shaped frame members 100 and 102 which are secured on opposite sides of the platform frame member 14 and may be constructed substantially identical to the rectangular frame members 30 and 28, respectively.

Again, an elongated triangular shaped lever arm 104 is pivotally secured at the upper rear corner thereof to the upper forward corner of the rectangular frame member 100. The lever arm bar 104 is substantially longitudinally disposed with the forward apex thereof being provided with an outwardly extending connection arm 106 which may be pivotally secured within the aperture 37 of the bracket member 34. An oppositely disposed substantially identical elongated triangular lever member 108 is pivotally secured at the upper rear corner thereof to the upper forward corner of the rectangular frame member 102. The lever arm member 108 is substantially longitudinally disposed with the forward end or apex corner thereof being provided with an outwardly extending connection rod 110 for being pivotally secured to a bracket member (not shown) which is substantially identical to the bracket member 34. A rearwardly extending elongated triangular shaped lever arm 112 is secured at the lower forward corner thereof to the lower rear corner of the rectangular shaped frame member 100, the rearwardly extending apex of the lever arm 112 being provided with an outwardly extending connection rod 114 which is slidably and pivotally disposed between the spaced bars 38 and 40 of the bracket means 36.

A substantially identical elongated triangular lever arm member 116 is pivotally secured at the lower forward corner thereof to the lower rear corner of the rectangular shaped frame member 102 by means of a horizontally disposed pivot pin 1 18. The rearwardly extending apex corner of the lever arm 116 is provided with an outwardly extending connection arm 120 which is slidably and pivotally disposed within a bracket means (not shown) which is substantially identical to the bracket means 36. One end of a horizontally disposed connector rod 122 is pivotally secured to the lower free corner of the lever arm member 108 by means of a horizontally disposed pin member 124, the opposite end of the connector rod 122 being pivotally secured to the upper free corner of the lever arm memher 116 by means of a horizontally disposed pin member 126. A longitudinally disposed connector rod 128 is pivotally secured at one end thereof to the lower free corner of the lever arm member 104 by means of a horizontally disposed pin 130, the opposite end of the connector rod 128 being pivotally secured to the upper free corner of the elongated lever arm 112 by means of a horizontally disposed pin 132.

An elongated traversely disposed torsion bar 134 is pivotally secured to the frame members and 102 and rigidly secured between the upper rear corners of the elongated lever arm members 104 and 108, the said torsion bar 134 providing the axle for pivoting the said lever arm members 104 and 108. Therefore, when the lever arm 104 or the lever arm 108 is rotated, simultaneous rotation of the opposite lever arm is accomplished by means of the torsion bar 134. Also, when rotation of the platform member 14 with its associated rectangular frame members 100 and 102 is rotated with respect to the lever arms 104, the lever arm 112 is rotated simultaneously in the opposite direction by means of the connector rod 128. Likewise when the lever arm 108 is rotated with respect to the frame member 102, opposite rotation is induced into the other lever arm 116 by means of the connector rod 122 connected therebetween.

It is therefore obvious, that the suspension and leveling means 98 operates substantially identically to the suspension and lever means of FIG. 1, hereinbefore described, with the exception that leveling across the frame member 14 is accomplished by means of a torsion bar 134 rather than by the hydraulic crossconnected cylinders 54 and 76 depicted in FIG. 1. It is also obvious, that the pivotal pin members 113 and 118 could be replaced by a second torsion bar (not shown) which would serve to partially relieve the torsion bar 134 of twisting motion induced therethrough.

Referring now to FIG. 3, reference character 135 generally indicates a suspension and leveling apparatus for use with a hydro-hoist platform as depicted in FIG. 1. The suspension and leveling apparatus 135 comprises an elongated lever arm member 136 which is longitudinally disposed and is provided with an outwardly extending connection rod 138 at the forward end thereof, the said connector rod 138 being pivotally disposed within the aperture 37 of the bracket means 34. The opposite end of the elongated lever arm 36 is provided with a rounded end portion 140, the said rounded end portion lying in a vertical plane. The rounded end portion 140 is provided with a plurality of gear teeth 142 around the outer periphery thereof. A second substantially identical elongated longitudinally disposed lever arm member 144 is provided with an outwardly extending connection rod 146 at the rear end thereof the said connection rod 146 being slidably and pivotally disposed within the slot formed between the horizontally extending spaced bars 38 and 40 of the bracket means 36. The forward end of the elongated lever arm 144 is provided with a rounded surface 148, the rounded end lying in a vertical plane and being provided with a plurality of gear teeth 150 around the outer periphery thereof.

The elongated bars 136 and 144 are disposed so that the gear teeth 142 of the bar 136 is in meshing engagement with the gear teeth 150 of the bar 144. An oppositely disposed elongated lever arm member 152 which is substantially identical to the elongated lever arm member 136 is provided with an outwardly extending connection rod 154 at the forward end thereof. The rear end of the lever arm member 152 is provided with a rounded surface 156, the said surface 156 lying in a vertical plane and being provided with a plurality of gear teeth 158 around the outer periphery thereof. A

rearwardly extending substantially identical'elongated lever arm member 160 is provided with an outwardly extending connection rod 162 at the rearwardly extending end thereof, the said connection rod 162 being slidably and pivotally disposed within a bracket means (not shown) which is substantially identical, to the bracket means 36 of FIG. 1. The forward end of the elongated lever arm member 160 is provided with a rounded surface 164, the said surface lying in a vertical plane and being provided with a plurality of gear teeth 166 around the outer periphery thereof. The lever arm members 152 and 160 are disposed in such a manner that the gear teeth 158 of the lever arm member 152 are in meshing engagement with the gear teeth 166 of the lever arm member 160.

The lever arm members 136 and 152 are pivotally secured to the frame member 14 by means of a traversely extending torsion bar axle 168, the said torsion bar axle 168 being secured to the rear ends of the lever arm members 136 and 152 at a point which is concentric with the rearwardly curved surfaces 140 and 156, respectively. Likewise, the forward ends of the lever arm members 144 and 160 are pivotally secured to the platform frame member 14 by means of a traversely extending torsion bar axle 170 which is secured to the forward ends of the lever arms 144 and 160 at a point which coincides or is concentric with the curved portions 148 and 164 of the lever arm members 144 and 160, respectively.

It is therefore obvious that when the lever arm members 136 and 152 tend to rotate with respect to the platform 14 simultaneous rotation between the said lever arms 136 and 152 is accomplished by means of the torsion bar axle 168. Likewise, rotation in the opposite direction of the lever arms 144 and 160 is accomplished by means of the gearing between the forwardly extending lever arms and the rearwardly extending lever arm members.

Therefore, when the hydro-hoist platform 14 is being either raised or lowered, the suspension and leveling apparatus 135 serves to keep the said platform 14 at a constant level attitude regardless of the load distribution on the platform or the uneveness of the hoisting forces exerted on the platform.

Referring to FIG. 6, reference character 318 generally indicates a suspension and leveling apparatus for use with a hydro-hoist platform as depicted in FIG. 1. The suspension and leveling apparatus 318 comprises an elongated triangular shaped lever arm 320 which is longitudinally disposed and is provided with an outwardly extending connection rod 322 at the forward end thereof, the said connection rod 322 being pivotally disposed within the aperture 37 of the bracket means 34. An oppositely disposed substantially identical elongated lever arm member 324 is longitudinally disposed on the opposite side of the frame member 14, the said lever arm 324 being provided with an outwardly extending connection rod 326 at the forward end thereof, the said connection rod 326 being pivotally disposed within an oppositely disposed bracket member (not shown) and substantially identical to the bracket means 34. The center portions of the rearwardly extending ends of the elongated lever arms 320 and 324 are connected together by means of a torsion bar 328 for simultaneous rotation therewith. The torsion bar 328 is pivotally mounted to the platform frame 14 near the center portion thereof.

A third elongated lever arm member 330, which is substantially identical to the lever arm member 320, is longitudinally/disposed directly behind the lever arm 320. The lever arm 330 is provided with an outwardly extending connection rod 332 at the forward end thereof, the said connection rod 332 being pivotally disposed within a bracket means (not shown) which is substantially identical to the bracket means 34. This second bracket means is secured to the dock 32 adjacent to the midportion of the frame member 14. An oppositely disposed triangular shaped elongated lever arm 7 334 having an outwardly extending connection rod 336 secured to the frame thereof is longitudinally disposed directly behind the elongated lever arm member 324. The connection rod 336 of the lever arm 334 is also pivotally secured to a bracket means (not shown) which is substantially identical to the bracket means 34. The center portions of the rear ends of the elongated lever arms 330 and 334 are connected together by means of a traversely disposed torsion bar 338 for simultaneous rotation therewith..The torsion bar 338 is pivotally secured to the rear portion of the platform frame member 14 in any well known manner (not shown).

One end of an elongated linkage rod 340 is pivotally secured to the upper rear corner of the lever arm member 320, the opposite end thereof being pivotally secured to the upper rear corner of the elongated lever arm 330. A substantially identical longitudinally disposed linkage rod 342 is pivotally secured at one end thereof to the lower rear corner of the elongated arm 320, the opposite end thereof being pivotally secured to the lower rear cornerof the elongated arm 330 to provide simultaneous rotation of the lever arm 330 with respect to the lever arm 320.

A third linkage rod 344 is secured at one end thereof to the upper rear corner of the elongated lever arm member 324, the opposite end thereof being pivotally secured to the upper rear corner of the elongated lever arm member 334. A fourth substantially identical linkage rod 346 is secured at one end thereof to the lower rear corner of the elongated lever arm 324, the opposite end thereof being pivotally secured to the lower rear corner of the elongated arm 334 to provide simultaneous rotation of the said lever arm 334 with respect to the lever arm 324.

In operation, when the platform 14 is submerged a boat may be driven or pulled up on to the cradle members 22 and 24 and the forward support member 26. The pontoons 18 and 20 may then be filled with air thereby raising the platform out of the water. Since the elongated lever arms 320 and 324 are connected by the torsion bar 328 they will rotate simultaneously and in the same direction as hereinbefore set forth. Also the torsion bar 338 will-serve to cause the elongated lever arms 330 and 334 to operate simultaneously in the same direction. Further since rotation of the lever arms 320 and 324 will cause similar rotation of the lever arms 330 and 334 due to the linkage rods 340, 342, 344 and 346, the platform 14 will of necessity maintain a constant attitude while being hoisted out of the water by the air filled pontoons l8 and 20 regardless of the load distribution on the platform 14 or the uneveness of filling the said pontoons 18 and 20 with air.

Referring now to FIG. 4, reference character 172 generally indicates a hydro-hoist apparatus which is particularly suited for carrying and hoisting rather large boats. However, the principle employed is suitable for large or small boats. Four substantially identical vertically disposed piers or suspension rods 174, 176, 178 and 180 are spaced in the shape of a rectangle each said pier being disposed at a corner of the said rectangle. A transversely disposed cross member 182 is slidably secured at one end thereof to the pier 174 by means of a slip ring 184, the opposite end of the said cross bar 182 being slidably secured to the pier 180 by means of a similar slip ring 186. A substantially identical cross bar 188 is secured at one end thereof to the pier 176 by means of a slip ring 190, the opposite end of the cross bar 188 being slidably attached to the pier 178 by means of a slip ring 192.

A pair of longitudinally disposed frame members 194 and 196 are secured between the cross members 182 and 188 to form the base platform generally indicated by reference character 200. A plurality of spaced intermediate frame bracing members 202 are connected between the frame members 194 and 196 to provide added rigidity for the platform 200. A pair of spaced cradle members 204 and 206 are longitudinally disposed and secured to the platform means 200 for carrying the stern portion of a boat thereon. A substantially V-shaped support member 208 is rigidly secured to the cross member 182 and is centrally disposed thereon for carrying the bow portion of a boat therein.

A vertically disposed hydraulic cylinder 210 is secured to the upper portion of the pier 172, the said hydraulic cylinder 210 having a downwardly extending connector rod 212, the lower end of the said connector rod 212 being secured to the cross member 182 adjacent to the slip ring 184. The hydraulic cylinder 210 is provided with a piston member 214 reciprocally disposed therein, the said piston member 124 being connected to the connector rod 212 for simultaneous movement therewith. A second substantially identical hydraulic cylinder 216 is vertically disposed and secured to the upper portion of the pier 176. The cylinder 216 is provided wtih a downwardly extending connector rod 218, the lower end of the said connector rod 218 being rigidly secured to the cross member 188 adjacent to the slip ring 190. A piston member 220 is reciprocally disposed within the hydraulic cylinder 216 and is connected to the connector rod 218 for simultaneous movement therewith.

A third substantially identical hydraulic cylinder 222 is vertically disposed and rigidly secured to the upper portion of the pier 178, the said hydraulic cylinder being provided with a downwardly extending connector rod 224, the lower end of the connector rod 224 being secured to the cross member 188 adjacent to the slip ring 192. A hydraulic piston member 226 is slidably disposed within the cylinder 222 and connected to the upper end of the connector rod 224 for simultaneous movement therewith. A fourth substantially identical hydraulic cylinder 228 is vertically disposed and secured to the upper portion of the pier 180, the said cylinder 228 having a downwardly extending connector rod 230, the lower end of the said rod 230 being secured to the cross member 182 adjacent to the slip ring 186. A hydraulic piston 232 is reciprocally disposed within the cylinder 228 and is connected to the connector rod 230 for simultaneous movement therewith.

The upper end of the hydraulic cylinder 210 is connected in open communication with the lower end of the hydraulic cylinder 228 by means of a hydraulic line 234. The upper end of the cylinder 228 is in open communication with the lower end of the hydraulic cylinder 222 by means of a hydraulic line 236. The upper end of the hydraulic cylinder 222 is operably connected to and in open communication with the lower end of the hydraulic cylinder 216 by means of a hydraulic line 238 and the upper end of the hydraulic cylinder 216 is oper ably connected to the lower end of the hydraulic cylinder 210 by means of a hydraulic line 240.

A plurality of transversely disposed pontoons 242 are secured to the bottom of the platform means 200, the upper portion of the said pontoons 242 being operably connected to a manifold member 244 by means of a plurality of air lines 246. The manifold 244 is then operably connected to an air pump or supply (not shown) by means of an air hose 248.

In operation, the pontoons 242 are partially, if not completely, filled with water and the platform means 200 is submerged beneath the water level, the connector rods 212, 218, 224 and 230 being fully extended. A boat (not shown) may then be either driven or pulled upon the platform 200, the stern of the said boat being supported by the cradle members 204 and 206 while the bow of the boat is supported by the V-shaped support member 208 as hereinbefore set forth. Air may then be supplied to the manifold 244 and from the manifold into the pontoons 242 by means of the air lines 246. The water that is in the pontoons 242 is then forced out of an aperture (not shown) along the bottom of the said pontoons thereby hoisting the platform 200 and the boat thereon out of the water. As the platform 200 rises the connector rod 212 of the cylinder 210 is forced upwardly thereby forcing the piston 214 upwardly which in turn causes hydraulic fluid to flow out of the top of the cylinder 210, through the line 234 and into the bottom of the cylinder 228. Likewise, fluid is forced out of the top of the cylinder 228 and into the bottom of a cylinder 222 by means of the line 236. Fluid is likewise forced out of the top of the cylinder 222 and into the bottom of the cylinder 216, the fluid in the top' of the cylinder 216 also being forced out and into the top of the cylinder 210.

. Since the cylinders 212, 216, 222 and 228 are substantially identical in size and volume a like amount of fluid is forced out of the top of each cylinder and into the bottom of the next succeeding cylinder thereby causing the pistons therein to move upwardly at an equal rate which in turn causes the platform member 200 to maintain a constant attitude regardless of the load distribution thereon or any uneveness in the filling of the pontoons 242 thereunder. A reverse action of the said hydraulic cylinder caused the platform member 200 to maintain a constant attitude while being lowered.

Referring now to P16. 5, reference character 250 generally indicates a platform suspension and leveling device which is suitable for use on a hydro-hoist boat lift similar to that of FIG. 4 hereinbefore described. Four upwardly extending piers 252, 254, 256 and 258 are arranged in a rectangular shape or pattern. A traversely disposed cross bar 260 is disposed between the piers 252 and 258 and slidably secured thereto by means of a pair of slip rings 262 and 264, respectively. A substantially identical forward cross member 266 is traversely disposed between the piers 254 and 256 and slidably attached thereto by means of a pair of slip rings 268 and 270, respectively. A pair of longitudinally disposed spaced frame members 272 and 274 are connected between the cross members 260 and 266 and rigidly secured thereto. The cross members 260 and 266 and the longitudinal frame members 270 and 274 form a platform hereinafter referred to by -reference character 276.

A plurality of pontoons (not shown) are secured to the bottom of the platform 276 in a manner similar to that shown for the platform 200 of FIG. 4. A pair of spaced cradle members 278 and 280 are secured to the cross member 260 for carrying the stern portion of a boat (not shown) thereon. A substantially V-shaped support 282 is centrally disposed on and secured to the cross member 260 for holding the bow portion of a boat (not shown) thereon. An elongated torsion bar 284 is traversely disposed with respect to the platform 276 and is rotatably mounted to a stable surface such as a boat dock floor (not shown) or the like. A pair of spool members 286 and 288 are rigidly secured to the torsion bar 284 and disposed near one end thereof in substantial alignment with the piers 252 and 254 for a purpose that will be hereinafter set forth. A substantially identical pair of spool members 290 and 292 are rigidly secured to the torsion bar 284 and located adjacent to the opposite end of the said bar and in substantial alignment with the piers 256 and 258 for a purpose that will be hereinafter set forth.

The pier 252 is provided with a pair of vertically spaced swivel mounted pulley members or sheaves 294 and 296, one located on either side of the slip ring 262. Likewise, a pair of vertically spaced sheave members 298 and 300 are secured to the pier 254 on either side of the slip ring 268. A similar pair of vertically spaced sheave members 302 and 304 are secured to the pier 256 on either side of the slip ring 270 and a pair of vertically spaced sheave members 306 and 308 are secured to the pier 258 on either side of the slip ring 264.

A first cable means 310 is secured at one end thereof to the slip ring 264 of the pier 258, thesaid cable being passed upwardly over the sheave member 306 and longitudinally then to the spool member 292. The cable 310 is then wrapped several times around the spool member 292 to prevent slippage thereon and passed longitudinally back through the sheave member 308, the opposite end of the said cable also being attached to the slip ring 264 of the pier 258. The cable 310 upon being attached to the slip ring 264 is stretched tightly so that there is little sag between the sheave member 306 and the spool member 292 and between the sheave member 308 and the spool member 292.

A second cable member 312 is secured at one end thereof to the slip ring 270 of the pier 256, the said cable being passed through the sheave member 302 and back to the spool 290. The cable member 312 is then wrapped several times around the spool member 290 to prevent slippagethereon, is passed through the sheave member 304, stretched tightly and then secured to the slip ring 270 of the pier 256. A third cable 314 which is substantially identical to the cable 310 and secured at one end thereof to the slip ring 262 of the pier 252, the cable being passed through the sheave 'memher 294 and to the spool member 286. The cable 314 is then wrapped several times around the spool member 286 to prevent slippage thereon. It is passed through the sheave member 296 and after being pulled tightly,

cable means 316 which is substantially identical to the cable means 312 is secured at one end thereof to the slip ring 268 of the pier 254, the cable then being passed through the sheave member 298 and to the spool member 288. The cable is wrapped several times around the spool member 288 to prevent slippage therearound and is passed through the sheave member 300 and after being drawn tightly, is attached back to the slip ring 268 of the pier 254.

lnsoperation, the platform 276 with its attached pontoons (not shown) are submerged in the water so that a boat (also not shown) may be either driven or pulled onto the platform cradle members 278, 280 and 282. Upon introducing air into the pontoon members, the platform means 276 will start to rise, being guided by the piers 252, 254, 256 and 258. As the platform rises, the guide rings or slip rings 262, 268, 270 and 264 having both ends of the cables 314, 316', 312 and 310 attached thereto will pull the said cables through the pulleys or sheaves that are mounted to the piers thereby causing the spools 286, 288, 290 and 292 and their associated torsion bar 284 to rotate in a clockwise direction as shown in FIG. 5. If one corner or one side of the platform 276 tries to lag or to advance faster than the other corners or side due to an out-of-balance condition of the boat on the platform 276, the said torsion bar 284 will transfer this extra load or light load to the other corners thereof by means of the cables thereby causing all four corners to either rise or descend with a constant attitude regardless of the load distribution on the platform or any out-of-balance condition caused by uneven filling of the pontoons (not shown) with air.

From the foregoing, it will be apparent that the present invention provides a platform leveling device which is particularly designed and constructed for maintaining a load carrying platform at a substantially constant attitude while it is either being raised, lowered or held in a static condition, regardless of the load distribution thereon or any uneveness of the hoisting means for the platform. The novel platform leveling device is economical and durable in construction and simple and efficient in operation.

Whereas, the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention.

What is claimed is:

1. In combination with a boat hoisting apparatus of the type having a pontoon-supported and vertically movable platform disposed for vertical up and down movement within a boat slip within a dock structure and wherein the vertical up and down movement is effected by the introduction of air into and the removal of air from, respectively, the pontoon portion of said apparatus, a platform leveling device comprising platform suspension means operably connected between the platform and the dock structure, and leveling means provided on the suspension means and operably connected to. the platform for maintaining a constant is attached back to the slip ring 262 of the pier 252. A

suspension means comprising a first pair of oppositely disposed lever arm members pivotally connected to the platform about a common transverse axis, one said lever arm member being disposed on each side of the platform, the said first pair of lever arm members being also pivotally secured to the dock structure, a second pair of oppositely disposed lever arm members pivotally secured to each side of the platform about a common transverse axis, said axis being spaced from the axis of the first pair of lever arm members, the said second pair of lever arm members being also pivotally secured to the dock structure, the first pair of lever arm members being pivotally connected to each side of the platform near the center portion thereof and extending forwardly therefrom, the forwardly extending ends thereof being pivotally connected to the dock structure and wherein the second pair of lever arm members are pivotally connected to each side of the platform near the rear portion thereof, said second pair of lever arm members extending forwardly from their pivotal connection, the forwardly extending ends thereof being pivotally connected to the dock structure, said leveling means comprising a first pair of longitudinally disposed vertically spaced linkage rods having one end thereof secured between the rear ends of the lever arm members on one side of the platform, said first pair of linkage rods vertically spaced on either side of the axis of rotation of the said lever arm members on one side of the platform, and an oppositely disposed second pair of longitudinally disposed vertically spaced linkage rods being secured between the rear ends of the lever arm members on the opposite side of the platform, said second pair of linkage rods vertically spaced on either side of the axis of rotation of the said lever arm members for providing simultaneous rotation of both lever arm members on one side of the platform and for providing simultaneous rotation of both lever arm members on the opposite side of the platform, said leveling means also comprising rotational transfer means for providing simultaneous rotation of both lever arm members of each pair of lever arm members.

2. A platform leveling device as set forth in claim 1 wherein the rotational transfer means comprises a first transversely extending torsion bar rotatably secured to the platform means and disposed between the first pair of lever arm members, the ends of the said first torsion bar being secured to the first pair of lever arm members at their axes of rotation with respect to the platform for providing simultaneous rotation of both lever arm members of the first pair of lever arm members and a second transversely extending torsion bar rotatably secured to the platform and disposed between the second pair of lever arm members, the ends of said second torsion bar being secured to the second pair of lever arm members at their axes of rotation with respect to the platform for providing simultaneous rotation of both lever members of the second pair of lever arm members. 

1. In combination with a boat hoisting apparatus of the type having a pontoon-supported and vertically movable platform disposed for vertical up and down movement within a boat slip within a dock structure and wherein the vertical up and down movement is effected by the introduction of air into and the removal of air from, respectively, the pontoon portion of said apparatus, a platform leveling device comprising platform suspension means operably connected between the platform and the dock structure, and leveling means provided on the suspension means and operably connected to the platform for maintaining a constant attitude of the platform during static conditions and during hoisting operations regardless of the load distribution on the platform and regardless of any unevenness of the hoisting by the hoisting means, said platform suspension means comprising a first pair of oppositely disposed lever arm members pivotally connected to the platform about a common transverse axis, one said lever arm member being disposed on each side of the platform, the said first pair of lever arm members being also pivotally secured to the dock structure, a second pair of oppositely disposed lever arm members pivotally secured to each side of the platform about a common transverse axis, said axis being spaced from the axis of the first pair of lever arm members, the said second pair of lever arm members being also pivotally secured to the dock structure, the first pair of lever arm members being pivotally connected to each side of the platform near the center portion thereof and extending forwardly therefrom, the forwardly extending ends thereof being pivotally connected to the dock structure and wherein the second pair of lever arm members are pivotally connected to each side of the platform near the rear portion thereof, said second pair of lever arm members extending forwardly from their pivotal connection, the forwardly extending ends thereof being pivotally connected to the dock structure, said leveling means comprising a first pair of longitudinally disposed vertically spaced linkage rods having one end thereof secured between the rear ends of the lever arm members on one side of the platform, said first pair of linkage rods vertically spaced on either side of the axis of rotation of the said lever arm members on one side of the platform, and an oppositely disposed second pair of longitudinally disposed vertically spaced linkage rods being secured between the rear ends of the lever arm members on the opposite side of the platform, said second pair of linkage rods vertically spaced on either side of the axis of rotation of the said lever arm members for providing simultaneous rotation of both lever arm members on one side of the platform and for providing simultaneous rotation of both lever arm members on the opposite side of the platform, said leveling means also comprising rotational transfer mEans for providing simultaneous rotation of both lever arm members of each pair of lever arm members.
 2. A platform leveling device as set forth in claim 1 wherein the rotational transfer means comprises a first transversely extending torsion bar rotatably secured to the platform means and disposed between the first pair of lever arm members, the ends of the said first torsion bar being secured to the first pair of lever arm members at their axes of rotation with respect to the platform for providing simultaneous rotation of both lever arm members of the first pair of lever arm members and a second transversely extending torsion bar rotatably secured to the platform and disposed between the second pair of lever arm members, the ends of said second torsion bar being secured to the second pair of lever arm members at their axes of rotation with respect to the platform for providing simultaneous rotation of both lever members of the second pair of lever arm members. 